Resin composition, process for producing the same and electrophotographic fixing member

ABSTRACT

A resin composition having a high adhesion between a resin layer and a metallic layer as well as an excellent durability, a process for producing the same, and an electrophotographic fixing member are provided. In the resin composition, a metallic layer is provided on a surface of a resin layer having a porous structure at least on the surface.

FIELD OF THE INVENTION

The present invention relates to a resin composition, a process forproducing the same, and an electrophotographic fixing member. Morespecifically, it relates to a resin composition which has a metalliclayer on a surface of a heat-resistant resin layer and which canadvantageously be used in a printed circuit substrate and anelectrophotographic member such as a fixing member, a process forproducing the same, and an electrophotographic fixing member.

DESCRIPTION OF THE RELATED ART

A laminate in which a thin film of a conductive metal such as copper oraluminum is laminated on a thin plate made of a heat-resistant resin ora thin plate in which a core member is impregnated with a heat-resistantresin has so far found wide acceptance as a printed circuit substrate.Further, in an image forming apparatus of an electrophotographic systemor an electrostatic recording system using a dry toner as well, a filmin which a heat-resistant resin is laminate with a metallic thin film issometimes used, in the form of an endless belt, as a fixing belt bywhich to fix a toner image with heat and pressure. In this fixing belt,an unfixed toner image formed by an electrophotographic process is fixedunder pressure by electromagnetic induction heating.

As the fixing belt, for example, an endless belt obtained by laminatinga film member made of a heat-resistant resin such as a thermosettingpolyimide, an aromatic polyimide (aramid) or a liquid crystal polymerand having a thickness of from 50 to 200 μm with a copper thin filmhaving a thickness of from 1 to 50 μm and forming thereon, as required,a heat-resistant elastic layer and further a heat-resistant releaselayer is used. The liquid crystal polymer is a polymer showing a liquidcrystal property in a solution state or in a molten state. A tropicliquid crystal polymer showing a liquid crystal property in a moltenstate has excellent properties such as a high strength, a high heatresistance, a low coefficient of linear expansion, a high insulation, alow moisture absorption and a high gas barrier property in particular.Accordingly, it has been increasingly used not only in productsutilizing a liquid crystal property but also in mechanical parts andfibers.

In the production of the film member in which the heat-resistant resinlayer is laminated with the metallic thin film, a method in which aheat-resistant resin film and a metallic foil are adhered with anadhesive and a method in which a metallic thin film is formed on aheat-resistant resin film by chemical plating or physical plating havebeen known.

However, in the method in which the adhesion is conducted with theadhesive as noted above, an adhesion strength is less reliable when themetallic thin film is repeatedly subjected to electromagnetic inductionheating. Also in the method in which the metallic thin film is formed onthe heat-resistant resin, it is generally difficult to firmly adhere aheat-resistant resin such as a polyimide or an aromatic polyamide(aramid) to a metallic thin film of copper. Accordingly, a technique forimproving an adhesion has been disclosed. For example, JP-A-5-299820proposes a technique in which a deposited metallic film is formed on apolyimide and an electron beam heat-deposited copper layer and anelectroplate copper layer are then insulated in this order.

JP-A-6-316768 discloses a technique in which for incorporating fluorinein a polyimide to make this fluorine an adhesion site, first etching isconducted with a hydrazine-containing aqueous solution and then secondetching is conducted with naphthalene-1-sodium to expedite adhesion ofcopper. JP-A-7-216225 discloses a technique in which a polyimideprecursor is mixed with a metallic powder to increase an adhesion with ametallic film through plating.

Meanwhile, when a heat-resistant resin is aft aromatic polyamide(aramid), JP-A-6-256960 proposes a technique in which etching isconducted with an aqueous solution containing hydrazine and an alkalimetal hydroxide and catalyst imparting treatment is then conducted forelectroless plating.

However, according to a method in which a heat-resistant resin is moldedand a metallic thin film is then formed thereon as in the ordinarytechniques, no satisfactory adhesion is obtained or a production processis hardly rationalized. On the other hand, when a liquid crystal polymeris used as a heat-resistant resin, a film member can directly behot-pressed with a metallic foil. However, the film member of the liquidcrystal polymer is generally oriented drastically in the molding andtends to be torn unidirectionally.

SUMMARY OF THE INVENTION

The invention has been made under these circumstances, and it intends toachieve the following aim upon solving the problems associated with theordinary techniques. That is, the invention provides a resin compositionhaving a high adhesion between a resin layer and a metallic layer and anexcellent durability, a process for producing the same and anelectrophotographic fixing member.

The invention provides a resin composition in which a metallic layer isprovided on a surface of a resin layer having a porous structure atleast on the surface.

Further, the invention provides an electrophotographic fixing memberusing the resin composition.

Still further, the invention provides a process for producing the resincomposition, which includes the steps of providing the porous structureat least on the surface of the resin layer and forming the metalliclayer on the surface of the resin layer.

BRIEF DESCRIPTION OF THE DRAWING

Preferred embodiments of the invention will be described in detail basedon the following FIGURE, wherein:

FIG. 1 is a schematic view showing an example of a fixing device havingan electrophotographic fixing member of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The invention is described in detail below. Both the resin compositionand the process for producing the same in the invention are explained.

The resin composition of the invention includes the metallic layer whichis provided on the surface of the resin layer having the porousstructure at least on the surface.

Many pores are present in the surface of this resin layer. Accordingly,when the metallic layer is formed on the surface of the resin layerhaving the pores, the metal is incorporated near the insides of thepores in the surface of the resin layer to be able to increase anadhesion (contact) area and obtain a so-called anchoring effect. Forthis reason, the resin composition of the invention has a high adhesionbetween the resin layer and the metallic layer and is excellent indurability.

The resin composition of the invention can be produced by forming themetallic layer on the surface of the resin layer having the porousstructure at least on the surface (process for producing the resincomposition in the invention). The details are described below alongwith a structure of each layer.

First, the resin layer is described.

In the resin layer, only a portion near the surface on which themetallic layer is formed may have a porous structure or the whole layermay have a porous structure. In view of a strength, it is preferablethat only the portion near the surface has the porous structure.

In the porous structure, many fine continuous holes are present from thesurface through the inside of the layer, and it is unnecessary that theholes are penetrated. The size of the pore (pore diameter) is, in viewof obtaining the desired adhesion (contact) area and anchoring effect,preferably 0.01 μm or more and 100 μm or less, more preferably 0.05 μmor more and 10 μm or less, further preferably 0.1 μm or more and 5 μm orless. When the size of the pore is less than 0.01 μm, the desiredanchoring effect might not be obtained. When it is more than 100 μm, thesurface of the metallic layer itself might be too rough.

The size of the pore here refers to an average value of a pore diameterobtained by observing the surface of the resin layer with a scanningelectron microscope and processing its image.

The material constituting the resin layer varies depending on a desireduse. For example, when it is used in a fixing member to be describedlater, it is preferably a heat-resistant material. Examples of theheat-resistant material include a polyester, polyethylene phthalate, apolyether sulfone, a polyether ketone, a polysulfone, a polyimide, apolyimideamide and a polyamide. It is preferable to use materialsclassified as a polyimide, an aromatic polyamide (aramid) and athermotropic liquid crystal polymer. The thermotropic liquid crystalpolymer includes a wholly aromatic polyester, an aromatic-araliphaticpolyester, an aromatic polyazomethine and an aromatic polyestercarbonate. Of these, a polyimide is especially preferable because a heatresistance and an abrasion resistance are high. With the use of thispolyimide, the resin composition can advantageously be applied to afixing member requiring a heat resistance and an abrasion resistance. Athermosetting polyimide is preferable. In the thermosetting polyimide,an imide group is directly bound to an organic group in a molecular mainchain, and this imide group serves as a recurring unit forpolymerization. An organic group includes, for example, an aliphaticgroup and an aromatic group. An aromatic group such as a phenyl group, anaphthyl group or a diphenyl group (including a group in which twophenyl groups are bound through a methylene group or a carbonyl group)provides good mechanical properties at a high use temperature. Apolyamic acid which is one polyimide precursor can be formed bypolycondensing equivalent amounts of an organic acid dianhydride and anorganic diamine in an organic polar solvent of room temperature.

The thickness of the resin layer can properly be selected depending onthe use. When it is used in a fixing member, it is preferably from 50 to150 μm. The respective resin layers may be formed of a single layer orplural layers. The respective layers may be made of the same material ordifferent materials.

In the invention, a method for forming the resin layer is notparticularly limited so long as at least the substitution has a porousstructure as stated above. For example, the following methods arepreferable.

(a) The resin layer is formed by coating a polyimide precursor solutionto form a polyimide precursor film (hereinafter referred to as a “PIprecursor film forming step”), coating a solvent substitution ratecontrol member having many through-holes on the surface of the polyimideprecursor film, contacting the polyimide precursor film with acoagulation solvent to form a polyimide precursor film having a porousstructure on the surface (hereinafter referred to as a “PI precursorprecipitation step”), and subjecting the polyimide precursor film havingthe porous structure on the surface to hot imidation to form a polyimideresin layer having a porous structure on the surface (hereinafterreferred to as a “PI resin layer forming step”) (this method ishereinafter referred to as a method (a)).

(b) A resin layer is formed by forming a bulk resin layer using a resinmaterial coating solution (hereinafter referred to as a “bulk resinlayer forming step”) and forming a porous resin layer on the surface ofthe bulk resin layer using a resin material coating solution containinga foaming agent (hereinafter referred to as a “porous resin layerforming step”) (this method is refereed to as a method (b)).

The method (a) is described below.

-PI Precursor Film Forming Step-

In the PI precursor film forming step, the polyimide precursor film isusually formed by coating the polyimide precursor solution on thesurface of the substrate. The polyimide precursor used in the solutionincludes a polyamic acid obtained from a diamino compound and atetracarboxylic dianhydride. Examples of the solvent that dissolves thepolyimide precursor include aprotic polar solvents such asN-methylpyrrolidone, N,N-dimethylacetamide, acetamide andN,N-dimethylformamide.

The polyimide precursor solution may contain, according to the purpose,a lubricant, a plasticizer, conductive particles, an antioxidant andother additives.

The polyimide precursor-containing solution can be obtained by, forexample, reacting an aromatic tetracarboxylic dianhydride with anaromatic diamine component in an organic polar solvent to form apolyimide precursor.

Typical examples of the aromatic tetracarboxylic acid includepyromellitic dianhydride, 3,3′,4,4′-biphenyltetracarboxylic dianhydride,3,3′,4,4′-benzophenonetetracarboxylic dianhydride,2,3,4,4′-biphenyltetracarboxylic dianhydride,2,3,6,7-naphthalenetetracarboxylic dianhydride,1,2,5,6-naphthalenetetracarboxylic dianhydride,2,2-bis(3,4-dicarboxyphenyl)ether dianhydride, tetracarboxylic estersthereof, and mixtures of the tetracarboxylic acids.

The aromatic diamine component is not particularly limited. Examplesthereof include p-phenylenediamine, m-phenylenediamine,4,4′-diaminodiphenyl ether, 4,4′-diaminophenylmethane, benzidine,3,3′-dimethoxybenzidine, 4,4′-diaminodiphenylpropane and2,2-bis[4-(4-aminophenoxy)phenyl]propane.

The amount of the polyimide precursor solution coated on the substratevaries with a desired film thickness. It is preferably from 200 to 1,800g/m². When it is less than 200 g/cm², the film thickness might beinsufficient. When it exceeds 1,800 g/m², the film thickness might beexcessive.

A method for coating a polyimide precursor solution is not particularlylimited. Examples thereof include a centrifugal forming coating methoddescribed in JP-A-57-74131, an inner surface coating method described inJP-A-62-19437, an outer surface coating method descanted inJP-A-6-23770, a dip coating method described in JP-A-3-180309 and aspiral coating method described in JP-A-9-85756. When a columnar orcylindrical substrate is used, it is preferable to use a dip coatingmethod described in JP-A-2002-91027.

The dip coating method is characterized in that a productivity is high.In a usual method, a coating film thickness is controlled with aviscosity of a coating solution and a withdrawal rate. The polyimideprecursor solution is problematic in that a viscosity is quite high at alow concentration. Accordingly, a wet thickness of a film after coatingis too high, so that the coating solution can hardly be coated to adesired film thickness. For this reason, it is especially preferable toapply a dip coating method described in JP-A-2002-91027 in which a floathaving a predetermined circular hole is put on a coating solution, and asubstrate is withdrawn through the circular hole. It is advisable that asize (diameter) of the circular hole of the float in the dip coatingmethod is properly adjusted by a desired film thickness. A thickness ofa wet film to be coated is controlled by a space between the circularhole and the substrate, and a dry film thickness is a product of a wetfilm thickness and a concentration of a coating solution. The space ispreferably from 1 to 3 times a desired wet film thickness. This isbecause a dry film thickness is not necessarily proportional to a wetfilm thickness because of a viscosity and/or a surface tension of acoating solution and shrinkage in curing.

-PI Precursor Precipitation Step-

In the PI precursor precipitation step, the solvent substitution ratecontrol member having many through-holes is coated on the surface of thepolyimide precursor film when contacting the polyimide precursor filmwith the coagulation solvent. The coagulation solvent is a solvent whichis insoluble in the polyimide precursor but compatible with the solvent(aprotic polar solvent) of the polyimide precursor solution.Accordingly, when the polyimide precursor film is contacted with thecoagulation solvent, the solvent (aprotic polar solvent) is eluted intothe coagulation solvent from the polymide precursor film and thecoagulation solvent is permeated therein instead. Since the polyimideprecursor is insoluble in the coagulation solvent, this polyimideprecursor is precipitated. When the polyimide precursor film iscontacted with the coagulation solvent, the solvent substitution ratecontrol member is coated on the surface of the polyimide precursor film,whereby the coagulation solvent is contacted with the polyimideprecursor film via only the through-holes of the control member. Only inthis contacted portion, the solvent (aprotic polar solvent) is elutedinto the coagulation solvent, and the coagulation solvent is permeatedinstead. In the polyimide precursor film, the pores are formed only inportions of the through-holes of the control member. Thus, the polymideprecursor film having the porous structure on the surface can be formed.After the polyimide precursor film having the porous structure on thesurface is formed, the solvent substitution rate control member isseparated.

The structure of the solvent substitution rate control member is notparticularly limited so long as it is coated on the surface of thepolyimide precursor film. Generally, a sheet is used. Specifically, forexample, a nonwoven fabric or a porous film made of a polyolefin such aspolyethylene or polypropylene, cellulose or polyethylene fluoride fibers(for example, Teflon (R)) is proposed. The solvent substitution ratecontrol member has many through-holes. The number or the size thereofvaries with a desired porous structure. It is advisable that the size(diameter) of the though-holes is determined to be larger than the sizeof the pore of the porous structure in the desired polyimide resinlayer.

Examples of the coagulation solvent include water, alcohols (such asmethanol and ethanol), hydrocarbons (such as hexane and heptane),ketones (such as acetone and butanone) and esters (such as ethylacetate). Water is preferable because it is easiest to handle.

With respect to a method in which the polyimide precursor film iscontacted with the coagulation solvent, a method in which a substratewith the polyimide precursor film formed thereinside is dipped in a bathfilled with the coagulation solvent is preferable. In this method, thepolyimide precursor film can uniformly be contacted with the coagulationsolvent. In this dipping method, in view of precipitating the polyimideprecursor at good efficiency to form the porous structure, it isadvisable that the coagulation solvent is stirred to expedite itspermeation into the through-holes in the solvent substitution ratecontrol member.

In the method in which the polyimide precursor film is contacted withthe coagulation solvent, the coagulation solvent may flow down or besprayed on the polyimide precursor film.

In the PI precursor precipitation step, the amount of the aprotic polarsolvent eluted from the polyimide precursor film varies with a time forcontacting the polyimide precursor film with the coagulation solvent.That is, the size or the depth (length) of the pore in the porousstructure can properly be controlled with this time.

Usually, the amount of the aprotic polar solvent eluted from thepolyimide precursor film to the coagulation solvent is increased withthe increase in the temperature of the coagulation solvent. Thus, thesize or the depth of the pore in the porous structure can properly becontrolled also with the temperature.

It is also possible that the amount of the aprotic polar solvent elutedfrom the polyimide precursor film can also be controlled by previouslymixing the coagulation solvent with the aprotic polar solvent, wherebythe size or the depth of the pore in the porous structure can properlybe controlled.

-PI Resin Layer Forming Step-

In the PI resin layer forming step, it is advisable that drying is firstconducted for removing the aprotic polar solvent. Preferable dryingconditions are that a temperature is from 20 to 120° C. and a time isfrom 10 to 60 minutes. It is also effective that hot air is fed to theinside of the cylinder. The drying temperature may be increased stepwiseor at a fixed rate.

When the drying is conducted by making a longitudinal direction of thesubstrate vertical, streak or unevenness might occur in a part of afilm. In this case, it is effective that rotation is further conduced bymaking the longitudinal direction of the substrate vertical. Therotational speed is preferably from 10 to 100 rpm. In some ratingdevice, the rotational speed may be higher or lower than this range. Adevice which conducts rotation by making the longitudinal direction ofthe substrate vertical is simpler in structure than a device whichconducts rotation by making the longitudinal direction of the cylinderlateral.

In the PI resin layer forming step, after the drying, the polyimideprecursor film is heated preferably at a temperature of approximately350° C. (more preferably from 300 to 450° C.) for 20 to 60 minutes forhot imidation to be able to form a polyimide resin layer. When thesolvent remains in the hot imidation, the polyimide resin layer might beswelled. Thus, it is advisable to completely remove the residual solventbefore the hot imidation. Specifically, it is preferable that before thehot imidation the film is heat-dried at a temperature of from 200 to250° C. for from 10 to 30 minutes and the temperature is then increasedstepwise or at a fixed rate for hot imidation.

By this method, the polyimide resin layer having the porous structure onthe surface can be formed.

The method (b) is described below. The method (b) is described accordingto the method in which the polyimide resin layer is formed using thepolyimide precursor solution, which is however not critical.

-Bulk Resin Layer Forming Step-

In the bulk resin layer forming step, the bulk resin layer (polyimideresin layer) can be formed as in the method (a) except that the solventsubstitution rate control member is not used in the PI precipitationstep. The “bulk” here is a word by which to distinguish the layer fromthe resin layer having the porous structure, and the bulk resin layermeans a resin layer free from the porous structure. The PI precipitationstep may be dispensed with as required.

-Porous Resin Layer Forming Step-

In the porous resin layer forming step, the bulk resin layer (polyimideresin layer) can be formed as in the method (a) except that a foamingagent is added to the polyimide precursor solution and the solventsubstitution rate control member is not used in the polyimideprecipitation step. In this miner, the porous resin layer can easily beformed by subjecting the resin material (polyimide precursor) to heatingtreatment (hot imidation) with the foaming agent. The PI precipitationstep may be dispensed with as required.

Specific examples of the foaming agent include “Cell Mike C191” (made bySankyo Kasei K.K., main component azodicarbonamide) and “Cell Mike 417”(made by Sankyo Kasei K.K., inorganic type).

When the resin layer is formed of plural layers as in the method (b), itis advisable that a lower resin layer is dried or half-cured andcompletely heated (hot imidation) with heating (hot imidation) of anupper resin layer. This method is preferable because the respectivelayers are melt-adhered to provide an excellent adhesion strength.

As in the methods (a) and (b), the resin material solution (polyimideprecursor solution) is usually coated when the resin layer is formed onthe surface of the substrate. The substrate is properly selectedaccording to the use form of the resin composition. For example, whenthe resin composition is used in the form of a film, a plate is used asa substrate. When it is used in the form of a belt, a columnar,cylindrical, elliptical columnar or elliptical cylindrical belt is used.As the material of the substrate, a metal such as aluminum, copper orstainless steel is preferable. At this time, it is also effective thatthe surface is plated with chromium or nickel or coated with afluororesin or a silicone resin or a release agent is coated on thesurface to prevent a polyimide resin from adhering to the surface. Sincethe rein composition can also be used without removing the substrate,the form or the material of the substrate can properly be selectedaccording to the use form of the resin composition.

The metallic layer is described below.

It is advisable that the metallic layer is made of copper, nickel,chromium, cobalt, iron, gold, silver, tin, zinc, aluminum or an alloythereof according to the use. It may be formed of a single layer orplural layers. When it is formed of plural layers, the respective layersmay be made of the same metal or different metals.

The metallic layer can preferably be formed by, for example, chemicalplating (such as electroplating or electroless plating) or physicalplating (such as vacuum deposition, sputtering or ion plating). Theseplatings are particularly preferable because a metallic film (layer) isgrown from inside the pore in the surface of the resin layer to be ableto make an adhesion strength quite high. As the metallic layer formed bythese platings, for example, a structure in which an electroless platedlayer and an electroplated layer are formed in this order is preferable.Especially when it is used in a fixing member and an electromagneticinduction heat generation system is employed as a heat source, thepresence of the copper-containing metallic layer is preferable becausethe heat efficiency is so high as to reduce the film thickness.Specifically, as the thus-formed metallic layer, a structure in which anelectroless plated nickel layer or an electroless plated copper layerand an electroplated copper layer are formed in this order ispreferable.

When, for example, an electroless plated metallic layer is formed in themetallic layer, it can be formed by reductively depositing a metallicion with a reducing agent such as formalin through electroless plating.When a metal is copper, a method described in JP-A-4-72070 orJP-A-4-186891 can preferably be employed. The thickness of the metalliclayer formed by electroless plating is preferably from 0.1 to 1 μm, morepreferably from 0.1 to 0.5 μm. When an electroplated metallic layer isformed, it is preferable that an electroless plated metallic layer ispreviously formed. Although the electroless plated metallic layer hasgenerally a high resistance, it is provided when a current has to bepassed through the metallic layer. Thus, the electroless plated metalliclayer serves as an electrode, and electroplating is conducted by ageneral method, whereby the electroplated metallic layer can be formed.The thickness of the electroplated layer is not absolutely definedbecause it varies with the metal used or the usage. For example, whenthe electroplated layer is used in a flexible circuit substrate andformed of copper, the thickness is preferably from 5 to 50 μm. When theelectroplated layer is used in a fixing member and formed of copper, thethickness is preferably from 3 to 20 μm. In case of nickel, it ispreferably from 8 to 60 μm. In case of iron, it is preferably from 10 to100 μm.

It is preferable that the thickness of the metallic layer is 10 μm orless. For example, when the resin layer is a polyimide resin layer, thepolyimide precursor resin layer is heated to form the polyimide resinlayer. Accordingly, the film is shrunk by approximately 10% (layerthickness). When the thickness exceeds 10 μm, wrinkling might occur. Forthis reason, the thickness of 10 μm or less little poses the problem ofwrinkling.

It is advisable that the metallic layer is formed while rotating thesubstrate lest the film thickness becomes uneven. Further, it isadvisable that the electrode in the electroplating is adapted tosurround the whole resin layer.

The form of the resin composition in the invention is properly selecteddepending on the usage. When it is used in a circuit substrate, a filmis preferable. When it is used in a fixing member, a belt is preferable.It is also possible that the resin composition is formed on acylindrical or columnar substrate and used as such in a fixing roller.

When the resin composition of the invention is used in a fixing member,an elastic layer and/or a release layer is further provided, asrequired, on the surface of the metallic layer. These layers can improvean image quality in fixing a color and prevent offset. Since the elasticlayer and the release layer are used in a fixing member, they arepreferably formed of a heat-resistant material.

As the elastic layer, an elastic layer containing a fluororubber as amain component and mixed with fluororesin particles or inorganicparticles of SiC or Al₂O₃ as required is proposed. Examples of thefluororubber include fluorine-containing elastomers such as a copolymerof vinylidene fluoride (VdF) as a main component and hexafluoropropylene(HFP), a three-component copolymer of the VdF-HFP copolymer andtetrafluoroethylene (TFE), and an alternating copolymer of TFE andpropylene. Further, a VdF-chlorotrifluoroethylene copolymer and amixture of a silicone rubber or a fluorosilicone rubber and thefluorine-containing elastomer containing VdF as a main component arealso available.

With respect to the release layer, fluororesins such aspolytetrafluoroethylene (PTFE), atetrafluoroethylene-perfluoroalkylvinyl ether copolymer (PFA) and atetrafluoroethylene-hexafluoropropylene copolymer (FEP) are preferable.For improving a durability and electrostatic offset, a carbon powder maybe dispersed in the release layer. The thickness of the release layer ispreferably from 4 to 40 μm.

The fluororesin film as the release layer is preferably formed by amethod in which its aqueous dispersion is coated on the surface of thelower layer and baked. When the adhesion of the fluororesin film ispoor, there is a method in which a primer layer is previously formed onthe surface of the lower layer by coating as required. Examples of thematerial of the primer layer include polyphenylene sulfide, a polyethersulfone, a polysulfone, a polyamideimide, a polyimide and derivativesthereof. Further, it is preferable to contain at least one compoundselected from fluororesins. The thickness of the primer layer ispreferably from 0.5 to 10 μm.

The resin composition of the invention can advantageously be used in anelectrophotographic fixing member (electrophotographic fixing member ofthe invention). A fixing device having the same is a fixing device of anelectromagnetic induction heat generation system, and it can have aknown structure. In the fixing device of the electromagnetic inductionheat generation system, an alternating current is passed through anelectromagnetic induction coil, whereby a magnetic flux penetratingthrough the metallic layer of the fixing member (resin composition ofthe invention) is generated and an excess current is generated in themetallic layer to allow heat generation and heat-fix a toner image atgood efficiency. Thus, in the fixing device of the electromagneticinduction heat generation system, the fixing member is repeatedly heatedwith the excess current. The satisfactory durability againstdelamination can be imparted by using, as a fixing member, the resincomposition of the invention having the excellent adhesion between theresin layer and the metallic layer. Especially in case of the belt,delamination tends to occur due to a resistance to sliding of a pressureroller and a nip portion. Accordingly, it is effective to use the resincomposition of the invention as the fixing member. An image formingapparatus having such a fixing device can also have a known structure.

Further, it can be applied as a transfer-fixing member which is one offixing members. This transfer-fixing maker is also called anintermediate transfer member. A toner image is once transferred onto theintermediate transfer member, the toner is heat-melted on theintermediate transfer member, and the toner image is heat-pressed on arecording medium. Thus, the transfer-fixing member conducts the transferand the fixing simultaneously. An image forming apparatus having such atransfer-fixing member can have itself a known structure.

An example of a fixing device having the electrophotographic fixingmember of the invention (resin composition of the invention) isdescribed below. However, this is not critical.

A fixing device shown in FIG. 1 has a heat-fixing belt member (fixingmember of the invention) 10 having a metallic layer, and a pressureroller 12. The heat-fixing belt member 10 is urged against the surfaceof the pressure roller 12 through a pressing member 14 to form a nipportion. The pressure roller 12 is provided with a driving unit (notshown). An electromagnetic induction coil 16 is mounted around thesurface of the heat-fixing belt member 10.

In the fixing device shown in FIG. 1, the pressure roller 12 is rotatedwith the driving unit (not shown), and the heat-fixing belt member 10 isalso rotated consequently. When an alternating current is passed throughthe electromagnetic induction coil 16, a magnetic flux penetratingtrough the metallic layer is generated in the heat-fixing belt member10, and an excess current is generated in the metallic layer for heatgeneration. When a recording medium 18 with an unfixed toner image Trecorded is passed through a nip portion between the heat-generatedheat-fixing belt member 10 and the pressure roller 12, the toner isheat-melted by the heat generation of the heat-fixing belt member 10 toconduct the fixing.

EXAMPLES

The invention is illustrated more specifically by referring to Examplesand Comparative Examples. However, the invention is not limited to theseExamples.

Example 1

An N,N-dimethylacetamide solution of a polyamic acid as a polyimideprecursor (trade name: U Varnish, made by Ube Industries, Ltd.,polyimide precursor solution) is used. A solid content is adjusted to20%, and a viscosity to approximately 1 Pa·s respectively.

A glass plate having a thickness of 0.2 mm and a size of 20×150 mm isused as a substrate, and dipped in the polyimide precursor solution bymaking the longitudinal direction vertical. Then, the plate is withdrawnat a rate of 100 mm/min to form a polyimide precursor film.

Subsequently, a solvent substitution rate control member (U Pore UP2015,gas permeability 550 sec/100 cc: made by Ube industries, Ltd.) havingmany through-holes is coated on the surface of the polyimide precursorfilm, dipped in water, and allowed to stand for 1 minute. When thesubstrate is withdrawn, the surface of the polyimide precursor film hasa porous structure with many pores.

Waterdrops are wiped out from the surface, and the substrate is then putinto a drying oven. The temperature is adapted to be gradually increasedsuch that the initial is 30° C. and 1 hour later, reaches 100° C. Afterthe drying, the film becomes transparent. The substrate is furtherheat-dried at 150° C. for 20 minutes and at 200° C. for 20 minutes tocompletely remove N,N-dimethylacetamide and water.

Thereafter, the heating is conducted at 350° C. for 30 minutes for hotimidation. As a result, a polyimide resin layer having a porousstructure on the surface is formed on the whole surface of thesubstrate. The film thickness of the polyimide resin layer is 0.5 μm andnearly uniform. The size of the pore in the porous structure is 0.8 μm.

Subsequently, electroless copper plating is applied to the surface ofthe polyimide resin layer to a thickness of 0.3 μm.

-Composition of an Electroless Plating Bath-

CuSO₄.5H₂O: 10 g/liter

EDTA.2Na: 30 g/liter

HCHO (37 mass %) solution: 5 g/liter

PEG#1000: 0.5 g/liter

-Electroless Plating Conditions-

Plating bath temperature: 65° C.

Stirring air method: air stirring

Plating time: 8 minutes

pH of a plating bath: 12.5

After the electroless plated metallic layer is formed by the electrolessplating as described above, copper is electroplated on the electrolessplated metallic layer to a thickness of 10 μm under the followingconditions to obtain an electroplated metallic layer.

Composition of an Electroplating Bath

CuSO₄.5H₂O: 120 g/liter

H₂SO₄: 150 g/liter

-Electroplating Conditions-

Plating bath temperature: 25° C.

Stirring method: air stirring

Plating condition: 2A/dm²

Plating time: 30 minutes

In this manner, the metallic layer including the electroless platedcopper layer and the electroplated copper layer is formed. Further, aheat-resistant primer (Teflon primer “855-021”, made by du Pont, aqueouspaint) is coated on the metallic layer, and a PFA dispersion (“500CL”,made by du Pont, aqueous paint) is then coated thereon. Calcination isconducted at 380° C. to form a release layer.

The thus-obtained film of the resin composition is processed into a beltto provide a heat-fixing belt. The resulting heat-fixing belt isinstalled on a fixing device shown in FIG. 1 as the heat-fixing beltmember 10, and an idling test is performed at 170° C. for 6 hours.Consequently, delamination does not occur in an interface between thepolyimide resin layer and the metallic layer (heat generation layer).

The pressure roller 12 of the faxing device shown in FIG. 1 is producedas follows.

-Production of a Pressure Roller-

A fluororesin tube having an adhesion primer coated thereinside andhaving an outer diameter of 50 mm, a length of 340 mm and a thickness of30 μm and a metallic hollow core are set in a mold. A liquid foamsilicone rubber is injected between the fluororesin tube and the core toa layer thickness of 2 mm. The silicone rubber is vulcanized and foamedby heat treatment at 150° C. for 2 hours to provide a rubber elasticity.In this manner, the pressure roller is produced.

Example 2

A fixing belt is produced as in Example 1 except that a polyimide resinlayer having a porous structure on the surface and having a thickness of20 μm is formed by properly changing a viscosity of a polyimideprecursor solution and a withdrawal rate of a substrate. When thisfixing belt is evaluated as in Example 1, delamination does not occur inan interface between the polyimide resin layer and the metallic layer(heat generation layer).

Example 3

A fixing belt is produced as in Example 1 except that a polyimide resinlayer having a porous structure on the surface and having a thickness of50 μm is formed by property changing a viscosity of a polyimideprecursor solution and a withdrawal rate of a substrate, and an elasticlayer [obtained by coating and drying a silane coupling agent “KBE 903”(made by Shin-etsu Chemical Industry Co., Ltd.) and then coating anddrying a liquid silicone rubber “KE1334” (made by Shin-etsu ChemicalIndustry Co., Ltd.): hardness 40° (JIS-A)] and a release layer (same asin Example 1) are further formed on a metallic layer in this order. Whenthis fixing belt is evaluated as in Example 1, delamination does notoccur in an interface between the polyimide resin layer and the metalliclayer (heat generation layer).

Example 4

A fixing belt is produced as in Example 1 except that a polyimide resinlayer having a porous structure on the surface and having a thickness of1.0 μm is formed into an endless belt by properly changing a viscosityof a polyimide precursor solution and a withdrawal rate of a substrateand using a cylindrical substrate. When the fixing belt is evaluated asin Example 1, delamination does not occur in an interface between thepolyimide resin layer and the metallic layer (heat generation layer).

Example 5

A fixing belt is produced as in Example 1 except that a polyimide resinlayer having a porous structure on the surface and having a thickness of20 μm is formed into an endless belt by properly changing a viscosity ofa polyimide precursor solution and a withdrawal rate of a substrate andusing a cylindrical substrate. When the fixing belt is evaluated as inExample 1, delamination does not occur in an interface between thepolymide resin layer and the metallic layer (heat generation layer).

Example 6

A fixing belt is produced as in Example 1 except that a polyimide resinlayer having a porous structure on the surface and having a thickness of20 μm is formed into an endless belt by property changing a viscosity ofa polyimide precursor solution and a withdrawal rate of a substrate andusing a cylindrical substrate, and an elastic layer [obtained by coatingand drying a silane coupling agent “KBE 903” (made by Shin-etsu ChemicalIndustry Co., Ltd.) and then coating and drying a liquid silicone rubber“KE1334” (made by Shin-etsu Chemical Industry Co., Ltd.): hardness 40°(JIS-A)] and a release layer (same as in Example 1) are further formedon a metallic layer in this order. When the fixing belt is evaluated asin Example 1, delamination does not occur in an interface between thepolyimide resin layer and the metallic layer (heat generation layer).

Example 7

A fixing belt is produced as in Example 1 except that a polyimide resinlayer is formed by the following method. When the fixing belt isevaluated as in Example 1, no delamination occurs in an interfacebetween the polyimide resin layer and the metallic layer (heatgeneration layer).

-Formation of a Polyimide Resin Layer-

A polyimide precursor film is first formed as in Example 1 except that asolvent substitution rate control member having many through-holes isnot coated on the polyimide precursor film, and this film is half-curedat 100° C. (bulk polyimide resin layer).

Subsequently, a polyimide precursor film is formed on the surface of thehalf-cured bulk polyimide resin layer as in Example 1 except that afoaming agent (“Cell Mike C-191”, made by Sankyo Kasei K.K.) is added toa polyimide precursor solution and a solvent substitution rate controlmember having many through-holes is not coated on the polyimideprecursor film. Hot imidation is conducted, and the bulk polyimide resinlayer and the porous polyimide resin layer are laminated in this order.Thus, the polyimide resin layer having the porous structure on thesurface is formed. The film thickness of the polyimide resin layer is 50μm and nearly uniform (bulk polyimide resin layer 40 μm, porouspolyimide resin layer 10 μm). Further, the size of the pore in theporous structure is 3.0 μm.

Example 8

A fixing belt is produced as in Example 1 except that an electrolessplated nickel layer is formed instead of the electroless-plated copperlayer in the metallic layer under the following conditions. When thefixing member is evaluated as in Example 1, delamination does not occurin an interface between the polyimide resin layer and the metallic layer(heat generation layer).

-Composition of an Electroless Plating Bath-

CuSO₄.5H₂O: 20 g/liter

NH₃.H₂O: 5 g/liter

HCHO: 10 g/liter

-Electroless Plating Conditions-

Plating bad temperature: 30° C.

Stirring method: air stirring

Plating time: 5 minutes

pH of a plating bath: 10.0

Comparative Example 1

A fixing belt is produced as in Example 1 except that a bulk polyimideresin layer is formed without coating a solvent substitution ratecontrol member having many through-holes on a polyimide precursor film.When the fixing belt is evaluated as in Example 1, delamination occursin an interface between the polyimide resin layer and the tic layer(heat generation layer) after 2 hours.

Comparative Example 2

A fixing belt is produced as in Example 4 except that a bulk polyimideresin layer is formed without coating a solvent substitution ratecontrol member having many through-holes on a polyimide precursor film.When the fixing belt is evaluated as in Example 1, delamination occursin all interface between the polyimide resin layer and the metalliclayer (heat generation layer) after 25 hours.

From Examples, it is found that in the resin composition of theinvention in which the metallic layer is provided on the polyimide resinlayer having the porous structure on the surface, the polyimide resinlayer and the metallic layer can be adhered mechanically firmly and thefixing belt using this composition does not cause the delamination dueto the repeated electromagnetic induction beat generation or theresistance to sliding of the pressure roller and the nip portion and hasthe excellent durability.

Thus, the invention provides the resin composition having the highadhesion between the resin layer and the metallic layer and theexcellent durability, the process for producing the same, and theelectrophotographic fixing member.

The entire disclosure of Japanese Patent Application No. 2001-282980filed on Sep. 18, 2001 including specification, claims, drawings andabstract is incorporated herein by reference in its entirety.

1. A fixing member in the form of an endless belt, said membercomprising: a resin layer having inner and outer circumferentialsurfaces, said resin layer having a porous structure on the outercircumferential surface, wherein only a portion being at or near saidouter circumferential surface has the porous structure and wherein theporous structure contains pores that do not penetrate through athickness of the resin layer, a metallic layer provided directly on saidouter circumferential surface, such that the metallic layer goes intopores of the resin layer, and an elastic layer and/or a release layerover the metallic layer.
 2. The fixing member as claimed in claim 1,wherein the resin layer contains a polyimide resin as a main component.3. The fixing member as claimed in claim 1, wherein the porous structureof the resin layer has an average pore size of from 0.01 μm to 100 μm.4. The fixing member as claimed in claim 1, wherein as the metalliclayer, an electroless plated layer and an electroplated layer are formedin this order.
 5. The fixing member as claimed in claim 1 wherein saidmetallic layer is plated on said surface of the resin layer.
 6. Thefixing member as claimed in claim 1, wherein the resin layer has athickness of from 50 μm to 150 μm.
 7. An endless belt comprising: aresin layer having a porous structure on a surface of the resin layer,wherein only a portion being at or near said surface of the resin layerhas the porous structure, a metallic layer provided directly on saidsurface of the resin layer, such that the metallic layer goes into poresof the resin layer, and an elastic layer and/or a release layer over themetallic layer.
 8. The endless belt as claimed in claim 7, wherein theporous structure contains pores that do not penetrate through athickness of the resin layer.
 9. The endless belt as claimed in claim 7,wherein the resin layer contains a polyimide resin as a main component.10. The endless belt as claimed in claim 7, wherein the porous structureof the resin layer has an average pore size of from 0.01 μm to 100 μm.11. An electrophotographic fixing device comprising: a fixing membercomprising (a) a resin layer having a porous structure on an outersurface of the resin layer, wherein the porous structure contains poresthat do not penetrate through a thickness of the resin layer, and (b) ametallic layer provided on said outer surface of the resin layer, suchthat the metallic layer goes into pores of the resin layer, and apressure roller in moving contact with said fixing member.
 12. Theelectrophotographic fixing device as claimed in claim 11, wherein anelastic layer and/or release layer is formed on the outer surface of themetallic layer.
 13. The electrophotographic fixing device as claimed inclaim 11, wherein said fixing member is a fixing belt.
 14. Theelectrophotographic fixing device as claimed in claim 11, wherein saidfixing member is a fixing roller.
 15. The electrophotographic fixingdevice as claimed in claim 11, wherein the resin layer containspolyimide resin as a main component.
 16. The electrophotographic fixingdevice as claimed in claim 11, wherein the porous structure has anaverage pore size of from 0.01 to 100 μm.
 17. The electrophotographicfixing device as claimed in claim 11, wherein said metallic layer isplated on the outer surface of said resin layer.
 18. Theelectrophotographic fixing device as claimed in claim 8, wherein themetallic layer comprises an electroless plated layer and anelectroplated layer, formed in this order on the outer surface of theresin layer.
 19. The electrophotographic fixing device as claimed inclaim 11, wherein only a portion being at or near said outer surface ofthe resin layer has a porous structure.
 20. The electrophotographicfixing device as claimed in claim 11, wherein said fixing member is inthe form of an endless belt.